Mechanical Ventilation Flashcards
What type of trigger variable may be more responsive to a patient breathing pattern
Flow triggered
What is the advantage and disadvantages of the volume cycled variable in mechanical ventilation?
Advantage: minute volume will remain constant to provide stable blood gases
Disadvantage: as lung compliance or resistance, worsen, PIP, and plateau pressure increase, which may cause barotrauma, or volutrauma.
What is the normal cycling variable in pressure support ventilation?
Flow cycling
What are the alarm settings for high-pressure, minimum exhaled volume, XL, low pressure, and oxygen in mechanical ventilation
-High pressure set 10 cm H2O above peak airway pressure
-Minimum exhaled volume set 100 mL below exhaled tidal volume.
-Low pressure set 10 cm below peak airway pressure
-Oxygen set 5% above and below FiO2 setting
What 3 devices, verify accuracy for volume, pressure, and flow
Volume-barometer,
Pressure-mercury or water manometer
Flow-Rotamater
What are the indications for continuous, mechanical ventilation?
Apnea
Acute ventilatory failure
Impending ventilatory failure -trend of rising, PCO2 and or decreasing Vt, Vc and MIP
Oxygenation
What bedside ventilator parameters can indicate mechanical ventilation is necessary
Vital capacity < 10 mL/kg
MIP <20 cm H2O
RR <8 or >20
Tidal volume < 5 mL/kg
VE >10 L/min
What physiological assessment or calculations indicate mechanical ventilation is necessary
Deadspace greater than 60%
Shunt greater than 20%
Static compliance < 25 mL/cn H2O
A-a DO2 >300 torr
What are the initial settings for mechanical ventilation?
Vt= 5-10 mL/kg of ideal body weight
Pressure (PC)= use plateau from VC or <35 cm H2O
RR=10-20
FiO2=40-60, set at lvl prior to ventilation
PEEP=2-6.. set at lvl prior to ventilation
What is the formula to determine ideal bodyweight weight?
50 kg + (2 x inches over/under 5 ft.
Increasing what ventilator parameter best increases alveolar ventilation
Tidal volume
How much dead space is in an inch of flex tubing
10 mL
The sum of anatomic and alveolar deadspace is called what
Physiologic deadspace
What is the frictional force that must be overcome during breathing called and what is the normal range?
 Airway resistance
0.6-2.4 cm H2O/L/sec. As high as 6 in intubated patients
What are two common causes and treatments for increased peak pressures?
Secretions in airway – suction
Broncospasm – broncodilators
What are the causes and suggested treatments of decreasing lung compliance (Cl)?
-Atelectasis
-Pulmonary edema
-ARDS
-Pneumonia
Increase PEEP and treat underlying cause
What ventilator control has the greatest influence on mean airway pressure (Paw)?
PEEP
What is the typical mean airway pressure in obstructive disease?
10-20 cm H2O
Normal: 5-10
ARDS: 15-30
Mean airway pressure (PAW) has the greatest impact on what life function
Oxygenation
How can you measure the work of breathing?
Change and pressure multiplied by the change in volume
What happens when work of breathing increases and respiratory muscles tire
Tidal volume decreases and respiratory rate increases
What are indications to switch a patient to SIMV
-Tachypneic patients to avoid hyperventilation
-To lower mean airway pressures.
-Used with peep to reduce barotrauma
Inverse ratio ventilation (IRV) improves, oxygenation and gas exchange and decreases PIP and PEEP levels. What patient criteria would indicate its use?
-patients requiring FiO2 over 60% and peeps greater than 15 cm H2O.
-PIP’s greater than 50 cm H2O
-Low PaO2 with decreased compliance
What ventilation mode is a form of spontaneous breathing at a positive pressure level, similar to CPAP, That occasionally releases the baseline pressure resulting in lower PIPs and mean airway pressure?
Airway pressure release ventilation (APRV)
What ventilator mode improves oxygenation using lower mean airway pressures
Airway pressure release ventilation (APRV)
What ventilator mode is a form of ventilation that keeps pressure at the lowest level by providing automatic breath to breath, pressure regulation while providing a preset volume
Pressure regulated volume control (PRVC)
What mode of ventilation has the characteristics or where pressure, volume and flow are proportional to the patient’s spontaneous efforts
Proportional assist, ventilation (PAV, or PAV+)
How would you initially determine settings for pressure support ventilation?
By calculating the patient’s airway resistance (PIP-Plateau).
What is the goal of pressure support ventilation
Overcome the resistance of the ventilator circuit and endotracheal tube during spontaneous ventilation
What mode of ventilation is indicated with PIP’s > 50 cm H2O or air leak syndromes to improve oxygenation Impatience with severe lung injury
High frequency oscillatory ventilation (HFOV)
What are the typical Hertz settings in high frequency oscillatory ventilation (HFOV)
3 to 15 Hz
1 Hz equals 60 cycles per minute
5 Hz equals 300 breaths per minute
In high frequency oscillatory ventilation, HFOV, what is the characteristics and goals of the ventilator parameters?
Very high, respiratory rates result in low alveolar pressure changes
Title volumes are very low (< 5 mL)
What are the two ways you would decrease PaCO2 in HFOV?
Primary-increase amplitude
Secondary-Decrease Hz frequency
When you wish to normalize a high PCO2 during mechanical violation, you should follow what order of?
- remove mechanical, dead space if possible
- Increase the tidal volume or PIP
- Increase the respiratory rate.
When you wish to normalize a low PaCO2, you should follow what order of steps
- evaluate the cause (hypoxemia, pain, fever and anxiety)
- decrease the respiratory rate
- Decrease the tidal volume or PIP.
When you wish to increase a low PaO2, you should follow what order of steps
- Increase FiO2 by 5 to 10% up to 60%.
- increase peep levels by 2 to 5 cm H2O until acceptable oxygenation achieved or unacceptable side effects occur
What are potential side effects of high levels of peep?
Decrease compliance
Decreased cardiac function
Barotrauma
Increased C(a-v)O2
What is the order of steps to decrease a high PO2?
- Decrease to less than .60
- Decrease PEEP
What are the ARDS net protocols?
1.Initial title of 8 mL/kg IBW and then reduce to 6 mL
2. Maintain plateau pressures < 30 cm of H2O
3. Consider permissive hypercapnia and subsequent respiratory acidosis.
What is the goal of a recruitment maneuver (RM)?
Sustained increase in pressures in along with the goal of opening as many collapsed lung units as possible
Please describe the most common recruitment maneuver (RM) for both peep and CPAP
Peep: increase peep to 40 cm of H2O for 40 seconds
CPAP: increase CPAP levels to 20 cm H2O for 20 seconds
If SPO2 rises and then falls, how many times can you consider repeating a recruitment maneuver?
Once
When should prone positioning be considered?
When FiO2 levels > .60 and PEEP levels are greater than 12 cm of H2O or when recruitment maneuvers have failed
Proning is successful in what percent of patient patients with ARDS and should improve PO2 within 30 minutes
75%
When successful, prone positioning, has what impact on PaO2, PaCO2, and shunt?
PaO2-increase by 10 to 50 torr
PaCO2-May decrease
Shunt-decreased by 12 to 25%
In normal loop graphics, what characteristic identifies an assisted breath?
A fish tail
What are high and low inflection points used for?
High – best volume
Low – best peep
What type of loop best identifies airway resistance, and what shape is characteristic of high airway resistance
A flow volume loop
Flattened ball
What does a broken loop in a ventilator graphic indicate?
An air leak
How can you identify water condensation in a flow volume loop?
Scalloped pattern
What type of ventilator graphic helps determine best peep, and volume?
A volume Pressure loop
What type of graphic is used to identify auto peep and how?
Scalar graphics.
The expiratory flow does not return to baseline before the next breath starts.
What are adverse effects of auto peep?
-Decreased cardiac output.
-Decreased blood pressure
-Increased intracranial pressure
-Over distention of alveoli resulting in barotrauma
-Difficulty triggering the ventilator
What are some reasons for an auto trigger in mechanical ventilation?
-Bounding pulse or cardiac movement
-Leaks in circuit or airway.
-Inappropriate trigger setting
-Condensation in circuit
What type of medication is used to decrease anxiety and promote relaxation and what are some names?
Sedatives, the ams and pams
Diazepam
What type of medication can reduce a patient’s ability to perceive sensation and what are some drug names?
Anesthetic
Propofol
ketamine
Etomidate
What type of medication reduces a patient sensation of Pain and what are a few common drugs
Analgesics & opioids
Morphine
Codeine
Fentanyl
Oxycodone, and all other dones
What are neuromuscular blocking agents used for?
Cause paralysis of skeletal muscle
Pancuronium and all onium meds
What is the best method to evaluate if a patient is ready for weaning
A spontaneous breathing trial with CPAP and with or without pressure support
What is the minimum and maximum time for a spontaneous breathing trial?
30 minutes up to 2 hours
What is the heart rate and respiratory rate criteria for termination of a spontaneous breathing trial. What are some other indicators?
Respiratory rate > 35 BPM for over five minutes
Heart rate greater than 130 or 20% over baseline
Blood pressure instability, Systolic blood pressure greater than 180 or less than 90
Cardiac arrhythmias
Oxygen saturation less than 90% or decreased 4% from baseline
pH less than 7.30
How long should you wait to repeat a spontaneous breathing trial (SBT)?
 24 hours
What types of drugs should be discontinued for a SBT?
Narcotics neuromuscular blocking agents
Anesthetics
How long after a ventilator wean has been initiated should an ABG be run?
20-30 minutes
Atelectasis can be common following extubation. What should be recommended to prevent it?
SMI or IPPB
After how long of failed weaning attempts is a patient considered ventilator dependent
Three months
What are the indications for noninvasive positive pressure ventilation
Acute exacerbation of chronic respiratory failure (COPD)
Congestive heart failure or pulmonary edema.
Severe dyspnea with a do not intubate order
What are the advantages of NPPV?
Avoids ventilator associated pneumonia
Avoids complications of an artificial airway
Avoids complications of mechanical ventilation
What are the recommended initial settings for NPPV?
IPAP: 8 to 12 cm H2O
EPAP: 4 to 6 cm of H2O
How do you calculate rapid shallow breathing index and what’s acceptable
RR / VT in L (ie. 0.4)
Less than 100
